Renal glycerol metabolism and the distribution of glycerol kinase in rabbit nephron

Abstract

Glycerol and dihydroxyacetone are metabolized by rabbit kidney-cortex tubules, isolated by collagenase treatment. Half-maximal concentrations of both substrates were determined with regard to uptake rates and product formation. Maximal uptake rates were 643 and 329 .mu.mol/h per g of protein for dihydroxyacetone and glycerol, respectively. Glucose and lactate were major metabolic products. Glycerol kinase, the enzyme catalyzing the 1st step in renal glycerol and dihydroxyacetone metabolism, was measured radiochemically as described by Newsholme et al (1967), and adapted for studies of the localization of this enzyme along the different structures of rabbit nephron. Glycerol kinase is located exclusively in the proximal segments, i.e., the proximal convoluted tubules and the pars recta, but is negligible in the other structures studied. The activities were close to the maximal dihydroxyacetone uptake rates measured in tubule suspensions.